A multiplicity of devices and analytical methods have been developed in an attempt to obtain fast and accurate quantitative analysis of a vast array of products which are manufactured subject to strict control of moisture. For example, certain products have a specific range of moisture which dictates the taste and/or texture of the product. Thus, once the consumer associates a specific taste and/or texture to the product the uniformity of that taste and/or texture becomes a hallmark to the product's long term acceptance and ultimate success. Furthermore, moisture content is a specific process control in food processing, waste water treatment and materials processing.
Typically, these products require the volatilization of moisture or the like from the substance for moisture determination. In recent years, conventional microwave heating has been employed in the methods to remove various volatiles such as moisture followed by calculations of the amount of moisture lost. Conventional microwave heating requires the use of high power levels for providing effective drying due to the conventional microwave ovens employing random direction T.sub.e waves as the dominant energy field for the drying process. As a result, these microwave ovens produce hot and cold spots, over heating edges and charring of the products being analyzed. The traditional attempts to avoid these problems was to use a mechanical device (e.g., a turntable) to move the sample in relationship to the cavity during heating or to use a mechanical stirrer to continually alter the mode pattern of the waves within the cavity. Even though these attempts were improvements to the conventional microwave oven, they failed to provide a satisfactory solution which provided fast and accurate moisture determination of the product without the degradation of the product due to these problems.
Thus, there continues to be a need for an efficient microwave moisture analyzer which offers uniformity of microwave heating and rapid moisture determining analysis. This is particularly important in light of the fact that most of the testing of products is related to process control in some form or another. Thus, the speed of the analysis and tests are hallmarks of high quality mass production. In addition, there is a need for a microwave moisture analyzer which provides timely feedback for maintaining tight tolerances of both the process and product produced thereby. Furthermore, a microwave moisture analyzer is needed which includes automated functions which simplify routine analysis thereby substantially eliminating the dependency of the result of the analysis on the skill and care exercised by the operator.
The following prior art reflects the state of the art of which applicant is aware and is included herewith to discharge applicant's acknowledged duty to disclose relevant prior art. It is stipulated, however, that none of these references teach singly nor render obvious when considered in any conceivable combination the nexus of the instant invention as disclosed in greater detail hereinafter and as particularly claimed.
______________________________________ PATENT NO. ISSUE DATE INVENTOR ______________________________________ 3,909,598 September 30, 1975 Collins, et al. 4,106,329 August 15, 1978 Takahashi, et al. 4,165,633 August 28, 1979 Raisanen 4,168,623 September 25, 1979 Thomas, Jr. 4,193,116 March 11, 1980 Funk 4,276,462 June 30, 1981 Risman 4,291,775 September 29, 1981 Collins 4,312,218 January 26, 1982 Eckles 4,316,384 February 23, 1982 Pommer, et al. 4,390,768 June 28, 1983 Teich, et al. 4,398,835 August 16, 1983 Athey, et al. 4,413,168 November 1, 1983 Teich 4,438,500 March 20, 1984 Collins, et al. 4,457,632 July 3, 1984 Collins, et al. 4,554,132 November 19, 1985 Collins 4,565,669 January 21, 1986 Collins, et al. 4,566,312 January 28, 1986 Collins, et al. 4,566,804 January 28, 1986 Collins, et al. 4,651,285 March 17, 1987 Collins, et al. 4,681,996 July 21, 1987 Collins, et al. 4,749,054 June 7, 1988 Virtanen, et al. 4,750,143 June 7, 1988 Heitz, et al. 4,753,889 June 28, 1988 Collins Re. 32,861 February 7, 1989 Collins, et al. 4,835,354 May 30, 1989 Collins, et al. 4,838,705 June 13, 1989 Byers, Jr. et al. 4,861,556 August 29, 1989 Neas, et al. 4,882,286 November 21, 1989 Neas, et al. 4,946,797 August 7, 1990 Neas, et al. 5,211,252 May 18, 1993 Henderson, et al. 5,215,715 June 1, 1993 Haswell, et al. Re. 34,373 September 7, 1993 Collins, et al. 5,318,754 June 7, 1994 Collins, et al. 5,420,039 May 30, 1995 Renoe, et al. 5,632,921 May 27, 1997 Risman, et al. ______________________________________